An "isotype" step junction is one in which the same impurity type dioping changes from one concentration value to another value. An it$-$n isotype doping proflile is show in figure. Using the energy$-$band diagrams, determine the built$-$in potential barrier.

$\backslash$table$[[$namber$,$evample$($inv$)],[1,9\mathrm{.}837],[2,72\mathrm{.}577],[3,59637],[4,79\mathrm{.}537],[5,9967]]$